No surprise, mobile devices lead the pack in a new study gauging the device demographics of full-game downloads. According to sales-tracker NPD Group, digital game downloads for mobile devices account for nearly half of all video game “full game” downloads. That’s discounting “microtransactions” or downloadable content like expansions or multiplayer maps, and by mobile devices, NPD means iPhones, Android phones, and whatever else falls under the column “mobile” (think games like Angry Birds, Doodle Jump, and Cut the Rope).

Mobile devices FTW? Not so fast. What’s missing from the study are contextual numbers like gross revenue or total spend. The gross revenue from 1,000 downloads of Angry Birds is roughly $1,000 (99 cents per copy sold). To hit the same amount, the PC version of Valve’s $50 Portal 2 needs only move 20 copies. You see where this gets tricky. The NPD numbers tell us something about mass game exposure, but not market health from an economic standpoint or followup exposure from a temporal one, i.e. how much time players spend with each game, fully-engaged.

NPD analyst Anita Frazier acknowledges this in the color commentary, noting that "full-game price points on mobile devices are generally lower than those for console and portables systems, so mobile's full game download unit share does not translate to a comparable level of consumer spend.”

NPD also found that 60 percent of over 8,000 study respondents purchasing games for mobile devices reported "spending the same or more on console and portable games,” while 40 percent said they spent less. NPD says this "makes sense since the games and devices provide for different types of gaming occasions and experiences.”

The most intriguing find: asked to choose between a physical or digital game (priced the same and released simultaneously) NPD found that 75 percent would pick physical. Why? Because they preferred owning a "real" copy (note that for console owners, physical copies can be used as "currency" at outlets like GameStop and Amazon that accept trade-ins, so the games-for-cash angle may be influencing that percentage).

The 25 percent remainder (count me among them) said the reason they picked digital was "the convenience of downloading at home and not having to go to the store."